The last time Anthony Armstrong wore a Dolphins uniform, he was an obscure practice-squad player. He returned Monday with a weightier résumé (51 receptions, 974 yards) and the burden of proving his breakout 2010 season with the Redskins was no aberration.

Armstrong, expected to provide a deep threat to Miami’s passing game, was one of four new Dolphins who participated in their first practice Monday after being claimed off waivers Saturday. And more help could be on the way. The Dolphins worked out receiver Jabar Gaffney on Monday, and he remains a possible addition. They also continue to consider available veteran cornerbacks.

Armstrong, 29, released by the Redskins on Friday, said “it’s kind of ironic to be coming back to South Florida, but I’m glad to be here. They told me they brought me here to play. I’m not the same guy that left in ’09. I know I’ve improved the past couple years. I’ve got to learn the offense and get on the same page as Ryan Tannehill.”

Armstrong said the Dolphins’ offense is similar to the Redskins’ “concept wise. The verbiage and tempo are completely different. Not having to go in a huddle is completely different.”

Undrafted out of Division II West Texas A&M in 2005, Armstrong played in the Intense Football League and the Arena League before spending 2008 on the Dolphins’ practice squad. Miami cut him in August 2009, and he joined the Redskins’ practice squad two months later.

Then, in 2010, the shocking breakout: Armstrong caught 44 passes for 871 yards, with his 19.8 per-catch average ranking behind only DeSean Jackson and Mike Wallace among receivers with at least 20 receptions.

His 2011 season started splendidly, with a touchdown in Week 1 against the Giants. But he lost playing time, didn’t catch another touchdown until Week 12 and closed the season with just seven receptions, along with three drops.

Among receivers who played at least 300 snaps last season, Armstrong caught the lowest percentage of passes thrown to him (7 for 25), though the Redskins quarterbacks shoulder considerable blame.

“The seven catches is not the type of receiver I am,” he said, declining to say what went wrong last season. “[In Washington], I was part of a receiving corps that people said was a weak link as well. They think the receivers here are weak. We have to show them they’re wrong.”

Offensive coordinator Mike Sherman said Armstrong has comparable speed to Clyde Gates, who was released Friday, and he hopes Armstrong’s “skill level will be at a high level.”

“All the things we heard about him, he’s supposed to be an extremely hard worker,” coach Joe Philbin said. “Obviously, he’s very fast.”

Among the Dolphins’ other weekend pickups:

• Troy Nolan could earn immediate playing time as a backup free safety. A seventh-round pick by Houston out of Arizona State in 2009, he played 30 games for the Texans the past two seasons, starting six, and snagged three interceptions (all in 2010).

His release was a surprise — including to Nolan — because his metrics were very good last season: Pro Football Focus ranked his play 26th of 168 safeties, with quarterbacks producing a 70.1 rating in his coverage area.

“He has some starting experience in Houston and has a chance to be a good player here,” Philbin said.

Nolan will face his former team on Sunday and is eager to “show them what they missed out on.” He’s also willing to share inside information on the Texans that could help his new team.

• Cornerback R.J. Stanford, who played with Dolphins cornerback Sean Smith for three years at Utah, is less established than Nolan. In 12 games as a rookie for Carolina last season, he allowed 12 of 17 passes thrown against him to be completed for 193 yards, one touchdown, one interception and a 103.3 quarterback rating against.

Stanford, who ranked 154th of 199 cornerbacks for 2011, intercepted Pat Devlin to end the Dolphins’ second exhibition game. Stanford said Dolphins general manager Jeff Ireland told him that “I made a few plays when we played them. He liked my effort.”

• Linebacker Sammy Brown, an undrafted rookie from Houston, finished with only one tackle for the St. Louis Rams in exhibition season.

As a college player, “they say I didn’t have enough effort. I agree with it,” he told The St. Louis Post Dispatch earlier this summer. “I didn’t go hard every play. But that’s over with.”

Despite the inconsistent effort, Brown produced big numbers at Houston: 76 tackles, 7 1/2 sacks and a Conference USA-leading 20 tackles for loss in 2010; and 93 tackles, 13 1/2 sacks and a nation-leading 30 tackles for loss last season. At 6-2 and 242 pounds, Brown runs well, with a very good 37-inch vertical leap.

“We thought he had some natural instincts and physical toughness and size to him that we liked,” Philbin said.